Dicyandiamide, formaldehyde and boric acid condensation product



Sept. 16, 195.8

| SELLET ETAL 2,852,490 n DICYANDIAMIDD, FDRMALDEHYDE AND BoRlc ACIDcoNDENsATIoN PRODUCT Filed July 21, 1954 REFLUX/NF/ 771115 HOL/RJINVEN-roRs [anni Sellef ATTORNEY United States Patent O M DICYANDKAMIDE,FORMALDEHYDE AND BORIC ACID CONDENSATION PRODUCT Lucien Sellet, SaddleRiver, N. J., and William O. Dawson, Amherst, N. H., assignors toJacques Wolf & Co., a corporation of New Jersey Application July 21,1954, Serial No. 444,832

3 Claims. (Cl. 260-69) This invention relates to the resinous reactionproduct of dicyandiamide, formaldehyde and boric acid.

z In our Patent 2,567,238, issued September 11, 1951, we describe acondensation product of dicyandiamide with 3.6-5 mols of formaldehyde.The condensation is effected in aqueous solution. Then the solution isspray dried. The product is a white powder that is readily soluble incold water and, in the dry form, is stable over long periods of time.

In our copending application Serial No. 277,292, filed March 18, 1952,now abandoned, we describe a related process and also a reaction productthat is less unstable in aqueous solutions and that, on standing,undergoes further polymerization and attendant thickening. In thiscopending application we react dicyandiamide with formaldehyde inaqueous solution and then introduce boric acid in free condition andcontinue the reaction.

In another eopending application Serial No. 363,689;

filed June 23, 1953, now issued as Patent 2,737,464, we describe, in oneexample, interaction of dicyandiamide and formaldehyde with boric acidpresent from the start and use the product to impregnato fibrousmaterials.

The present application is a continuation in part of the said copendingapplications.

Briey stated, the present invention comprises the process of and theproduct resulting from introducing boric acid in free condition intomixed aqueous dicyandiamide and formaldehyde, the boric acid beingintroduced in advance of any substantial initial reaction between thedicyandiamide and formaldehyde, and maintaining contact of the threereactants initially at a pH on the acid side of 7 until reaction issubstantially complete. In commercial practice, the three reactants aremixed in aqueous solution before the temperature of the mix is raised tothat at which reaction becomes rapid and the elevated temperature ofrapid reaction is maintained until the pH, below 7 at the start, risesand then ceases to rise rapidly. Y

The change in pH during the reuxing at about 95 C. is illustrated in theligure of the drawing to which reference is made.

The dicyandiamide ordinarily used is the commercial dry material. Theformaldehyde is used in its aqueous solution such as 37% formalin or anyone of the commercial aqueous compositions including also a loweraliphatic alcohol or paraformaldehyde may be used. The boric acid issupplied to advantage in crystal form.

The proportion of the formaldehyde should be Within.

the range 3.55 mols for 1 mol of the dicyandiamide. When proportions offormaldehyde below 3.5 are used, then there is haziness or insolubilityin cold water, either of which is objectionable, particularly inapplications of the product for impregnating fibrous materials. There isno need of using larger, uneconomical proportions of the follow.

2,852,490 Patented Sept. 16, 1958 ICC formaldehyde than 5 mols, as the 5mols give good, clear solutions of adequate stability on standing.

The proportion of boric acid used is 0.1-1 mol for 1 of dicyandiamide.Below 0.1 mol, haze or instability results, instability being evidencedby gelling or objectionable rate of thickening on storage of the aqueoussolution. More than 1 mol of the boric acid, on the other hand, isunnecessary for satisfactory properties of the reaction product.

With proportions within the ranges stated, the products of the inventionare resins that are soluble in either hot or cold water to givesolutions that are clear and that remain clear without gelling orover-thickening for periods up to several months or longer.

Proportions of boric acid within the upper part of the range 0.l-1 molgive stability for longer periods of time than proportions near thelower limit. Solutions with 1 mol have remained stable for a year.

The reaction of the three components is effected in aqueous solutionthat initially is acid. To obtain a rate satisfactory in factoryoperations, the reaction is conducted at an elevated temperature, aswithin the range -100 C. Autoclave temperatures up to about 140 C. maybe used, but there is no necessity of using any temperature above thatof refluxing of the mixture at atmospheric pressure, this being about C.In general, it will be understood that the rate of reaction increaseswith the temperature. Under reuxing conditions the reaction isordinarily complete in about 3-4 hours, 3.5 being adopted as the periodof heating in regular operations.

In spite of the previous observations that an alkaline catalyst isdesirable in accelerating the condensation of dicyandiamide withformaldehyde, we now find that the introduction of the boric acid makesthe incorporation of any alkaline catalyst of condensation unnecessaryfor a good rate of reaction. In fact, the introduction of the alkalinecatalyst or any inorganic buffer for boric acid is undesirable in thepresent process.

The invention will be illustrated in greater detail by description inconnection with the specific examples that In these examples andelsewhere herein, 1 mol of dicyandiamide was supplied in the form of 84parts of crystals, each mol of formaldehyde by 81 parts of its 37%aqueous solution, and each one-tenth mol of boric acid by 6.2 parts, allproportions unless otherwise stated being expressed as parts by weight.

Examples 1-3 In each preparation of this section, water was added inamount required, if any, to make the total volume of the formaldehydesolution and added Water equal to 300 ml. for each gram molecule ofthedicyandiamide.

Allthe mixes were made complete including the boric acid "before heating4was undertaken. Then they were raised to reuxing and kept at thattemperature of about 95 C. for 3.5 hours. At that time the pH had risenas illustrated in the drawing from less than 7 at the start to higherlevels and had become practically constant within the limit ofexperimental errors due to minor variations in the processing includingloss of vapor during reuxing and sampling. The heating was thendiscontinued.'

The following table shows the molar proportions; the pHs, to the firstdecimal place, at the start of the refluxing and also after the 3.5hours reiluxing; and also the solubility of the product in water.

The unnumbered tests or first three runs show the unsatisfactorysolubility that results with formaldehyde proportions -below 8,5.

Example Proportlons for 1 pH of Solution Product Soluble to No. mol dleyClear Solution HCH() HsBOx At'the Alter Cold Hot Water Start 3.5 Hrs.

if 11 4.o 15.5; refrain. 2 1 4.01 15.9 No..0 Nearlyjcom- I. pletel'y. `31 4.5- 6.6 No.-- Yes. 1- 3.5` 1` 4.7 f1.6- Yes.-. Yes 2 4 1 5.4 6.9 YesYes. 3 5 '1V 4.9i Ye's-- Y'e's lrhe H values for produ-ets made wit-h 1and 2 'mors of formalde yde were determined at the end of 3 hours.0bservations of solubility made at the end of 3% hours show, however,that these products were not 4completely soluble evenin hot Water,thereactiron products in b oth .cases settling out in part at least aswhite sticky material.

When the 'producir solutions were 'diluted vto concentra tions of 'byweight, before 't-he `pH tests were made upon them, the pHs found wereconsiderably higher than for the full strength solutions. Thus 'the nal-p'Hs for Examples l and 3 in 10% solutions were 8.1 and 7.9,respectively. v

It will be noted that the products with 3.-'5-5 mols of formaldehydewere soluble and gave clear solutions in cold water, Products madesimilarly but with 3 mols of formaldehyde were insoluble in cold water.y Y

All of the .products of the several, preparations of the above tablewere cation active at the end of the heating period. l A

After cooling, the products of -Examples 1-3 were ready for shipping fintheir cold aqueous solutions, either at full strength or after dilution,and are useful in the impregnation of leather and other fibrousmaterials as described in our said application Ser. No. 363,689, asareproducts of Examples 4 and 5.

Example 4 The vprocedure of Example 2 was followed except that theproportion ofboric acid was reduced to 0.1 mol 'for 1 mol of thedicyandiamide and 4 mols of formaldehyde.

The pH at the start of the refluxing was 6.1, after 2 hours refluxing 7.-9, 4after V3 .5 hours 8.0, and after 4 hours 8.1, when the reuxing wasstopped.

The product was soluble Vincold water to a clear solution and stable onaging for the importantcommercial period between manufacture, shippingand reasonable storage before use. The :product was cation active.

Like results were 'obtained when 0.25 mol of boric acid and 0.50 jmolwere substituted in turnfor the 0.1 mol above. pI-Is were 6.1 Vat thestart and 7 .2 after 3.5 hours with 0.25 mol of 1.boric lacid used and6.3 and 7.3 for 0.5 mol. In general, 'stability is improved as theproacid powder (2 mols) were mixed with 350 lbs. of water and the wholemixture heated to a boil until the boric acid dissolved and then reuxedfor 3.5 hours at a temperature between 92" and 95 C.

All the products of Examples 1-5 are resins that are soluble in cold orhot water, to form clear solutions that are dilutable up to 10 volumesor more with water without precipitation and that are stable(non-gelling) on storage for periods up to several months or longer,even at winter temperatures.

In general, we consider that the boric acid, added at or before thestart ofthe condensation vof dicyandiamide and boric acid, Acombineswith lbasic groups as basicity develops progressively during thereaction. This contiii'uing laction of the boric acid is more effective,.per unit proportion of the boric -aeid used, -in preventing jovercondensation and ultimate thickening up or actual gellingof thesolution, than is the Vsaine weight ofboric acid added after thedicyandiamide yand formaldehyde have been already condensed together. Weuse, therefore, a smaller proportion of boric acid for a given extent ofstabilization than .is required when the boric acid is added after thecondensation between vthe dicyandiamide and formaldehyde has beenelfected.

Tt will be 'understood that it is intended to cover all 'changes andmodicat'ions of 'the examples of the invention herein chosen for thepurpose of illustration which do not constitute departures from Vthespirit and scope of Vthe invention.

What we 'claim is:

1. The condensation product of dicyandiamide, fortnld'ehy'de, and boricacid in the molecular proportions of portion yof boric acid is increasedwithin the range 0.1-1 mol.

Example 5 As described in our copcnding application 'Sei'. No. 6

1, 3;'5-5 'and 0.1-1, respectively, the product being resinous, solublein both cold and hot water, non-precipitating on extreme dilution of theaqueous solution, and stable in 'the aqueous solution on standing andbeing the product 'of heating, a't a pH below 7 initially, a mixture ofthe dicyandiamide, formaldehyde, and boric acid in aqueous solutionuiitil the pH ofthe 'solution rises and becomes .practically constant.

Y :2. In making a resin that is soluble in cold water and stable inaqueous solution, the process which comprises forming a mixture ofdicyandiamide, formaldehyde, and boric 'acid in aqueous solution and inthe molecular proportions 'of 1, 3 5-5 'and 0.1-1, respectively, andmaintaining contact between the materials of the mixture at 'an elevatedtemperature and at a pH initially below 7 until vthe pH rises andbecomes .practically constant vand the resulting clear solution forms noprecipitate on extreme dilution with cold water.

3. The process of claim 2 which includes maintaining the said contact atapproximately the temperature of refluxing 'of the aqueous solution anduntil the pH rises to a level above about 6.5 and becomes practicallyconst'ant.

References Cited in the file of this patent UNrrED STATES PATENTS

1. THE CONDENSATION PRODUCT OF DICYANDIAMIDE, FORMALDEHYDE, AND BORICACID IN THE MOLECULAR PROPORTIONS OF 1, 3.5-5 AND 0.1-1, RESPECTIVELY,THE PRODUCT BEING RESINOUS, SOLUBLE IN BOTH COLD AND HOT WATER,NON-PRECIPITATING ON EXTREME DILUTION OF THE AQUEOUS SOLUTION, ANDSTABLE IN THE AQUEOUS SOLUTION ON STANDING AND BEING THE PRODUCT OFHEATING, AT A PH BELOW 7 INITIALLY, A MIXTURE OF THE DICYANDIAMIDE,FORMALDEYHYDE, AND BORIC ACID IN AQUEOUS SOLUTION UNTIL THE PH OF THESOLUTION RISES AND BECOMES PRACTICALLY CONSTANT.